GSoC PRU device tree overlay

[Vijay Kumar Banerjee]

On Mon, May 27, 2019 at 1:24 PM Nils Hölscher <nilhoel1 at gmail.com> wrote:

> Hi,
>
> I tried to rout the PRUs pins via device tree overlay this week.
> Sadly I wasn't able to produce results on linux with this method.
> Please check my blog post concerning this issue.
>
> https://nilshoel.home.blog/2019/05/27/setting-up-prus-pins-via-device-tree-files/
>
> It would be great if someone having experience with device tree overlay
> could get me some feed back.
> I will now move on to setting up RTEMS and porting the drivers.
>
> Hello Nils,

I read your blog and had a look at the overlay. From first look at the
overlay I noted that you're using `target-path`. I think target-path holds
a path string like "/path" instead of a reference to your pruss. Maybe
there should be a `target` field and you'll have to seth the target path
manually or just remove it if you're not using it.

A few pointers that helped me in general, to get an overlay working :
 * always check for the -@ option while compiling with dtc
 * before applying using a bootscript in u-boot, it might be a good
    idea to use the fdtoverlay tool ( in linux host) and apply it on your
    host system.
 * If it applies well, then just decompile the dtb with the
    dtc and have a look at the device you were targeting, if your changes
    look nice and so far you didn't get any error during the building, open
    u-boot and manually apply overlay using `fdt apply`.

With a quick look these pointers might be helpful. I'm working on porting
the i2c stack from FreeBSD to RTEMS and have used an overlay for the
path and compatibility. Hope these pointers were of some help.
I can explain any of the points above if they're not clear and you can post
the error log here as well ( if you luckily get proper error messages  ;-) )

Regards,
Vijay

> Best regards,
> Nils Hölscher
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